Hey I saw your post and wanted to fill you in on the legalities of the situation. I'm a commercial real estate agent in Tacoma and wanted to inform you on how it works. The post that talked about the river being navigable by boat is correct!! If the river is navigable by boat, the property owner owns to the high water mark, aka the flood plain. If it's not navigable by boat, the adjoining property owners own the "the said" middle of the river. I got into an argument with a property owner telling me I was trespassing on his property. When I explained that I wasn't and if he didn't believe me he could call the sheriff and he would explain it to him, he backed away and let me go about my business. This situation seems to come up a lot these days and it's important to be informed on the law. Let me know if there are any questions.